The two Rubik-like puzzles, Sixteen and Twiddle, now support an

additional configuration parameter, which is the number of shuffle
moves. By default the grid will be fully shuffled so that you need a
general solution algorithm to untangle it, but if you prefer you can
request a grid which has had (say) precisely four moves made on it,
and then attempt to exactly reverse those four moves.

Currently this feature is only available from the Custom box, and
not in any presets.

[originally from svn r5769]

1 files changed, 65 insertions, 3 deletions

diff --git a/puzzles.but b/puzzles.but
index 7d90f43..5f8bff4 100644
--- a/puzzles.but
+++ b/puzzles.but
@@ -415,9 +415,41 @@ Right-clicking will move it in the opposite direction.
 
 \H{sixteen-params} \I{parameters, for Sixteen}Sixteen parameters
 
-The only parameters available from the \q{Custom...} option on the
-\q{Type} menu are \e{Width} and \e{Height}, which are
-self-explanatory.
+The parameters available from the \q{Custom...} option on the
+\q{Type} menu are:
+
+\b \e{Width} and \e{Height}, which are self-explanatory.
+
+\b You can ask for a limited shuffling operation to be performed on
+the grid. By default, Sixteen will shuffle the grid in such a way
+that any arrangement is about as probable as any other. You can
+override this by requesting a precise number of shuffling moves to
+be performed. Typically your aim is then to determine the precise
+set of shuffling moves and invert them exactly, so that you answer
+(say) a four-move shuffle with a four-move solution. Note that the
+more moves you ask for, the more likely it is that solutions shorter
+than the target length will turn out to be possible.
+
+\H{sixteen-cmdline} \I{command line, for Sixteen}Additional
+command-line configuration
+
+The limited shuffle parameter, described in \k{sixteen-params}, is
+not mentioned by default in the game ID (see \k{common-id}). So if
+you set your shuffling move count to (say) 4, and then you generate
+a normal 4\by\.4 grid, then the game ID will simply say
+\c{4x4:}\e{numbers}. This means that if you send the game ID to
+another player and they paste it into their copy of Sixteen, their
+game will not be automatically configured to use the same shuffle
+limit in any subsequent grids it generates. (I don't think the
+average person examining a single grid sent to them by another
+player would want their configuration modified to that extent.)
+
+If you are specifying a game ID or game parameters on the command
+line (see \k{common-cmdline}) and you do want to configure the
+shuffle limit, you can do it by suffixing the letter \cq{m} to the
+parameters, followed by the move count as a decimal number. For
+example, \cq{sixteen 4x4m4} will start up Sixteen with a problem
+guaranteed to be soluble in four moves or fewer.
 
 
 \C{twiddle} \i{Twiddle}
@@ -475,6 +507,36 @@ you ask for an orientable puzzle, each tile will have a triangle
 drawn in it. All the triangles must be pointing upwards to complete
 the puzzle.
 
+\b You can ask for a limited shuffling operation to be performed on
+the grid. By default, Twiddle will shuffle the grid so much that any
+arrangement is about as probable as any other. You can override this
+by requesting a precise number of shuffling moves to be performed.
+Typically your aim is then to determine the precise set of shuffling
+moves and invert them exactly, so that you answer (say) a four-move
+shuffle with a four-move solution. Note that the more moves you ask
+for, the more likely it is that solutions shorter than the target
+length will turn out to be possible.
+
+\H{twiddle-cmdline} \I{command line, for Twiddle}Additional
+command-line configuration
+
+The limited shuffle parameter, described in \k{twiddle-parameters},
+is not mentioned by default in the game ID (see \k{common-id}). So
+if you set your shuffling move count to (say) 4, and then you
+generate a normal 3\by\.3 grid, then the game ID will simply say
+\c{3x3n2:}\e{numbers}. This means that if you send the game ID to
+another player and they paste it into their copy of Twiddle, their
+game will not be automatically configured to use the same shuffle
+limit in any subsequent grids it generates. (I don't think the
+average person examining a single grid sent to them by another
+player would want their configuration modified to that extent.)
+
+If you are specifying a game ID or game parameters on the command
+line (see \k{common-cmdline}) and you do want to configure the
+shuffle limit, you can do it by suffixing the letter \cq{m} to the
+parameters, followed by the move count as a decimal number. For
+example, \cq{twiddle 3x3n2m4} will start up Twiddle with a problem
+guaranteed to be soluble in four moves or fewer.
 
 \C{rectangles} \i{Rectangles}